Fluid control valves are used in a wide variety of processing systems, such as oil and gas pipelines and processing lines, to control the flow of fluids, including liquids and/or gases, in various lines in many industrial and non-industrial uses. In safety and/or functional critical applications, substantial maintenance is required to assure that the control valve performs properly at all times and thereby reduce losses associated with valves that are not functioning properly. Such maintenance includes both periodic preventative maintenance and repair of malfunctioning valves. Therefore, it is common to diagnostically check such fluid control valves while installed in the processing system so that operational problems can be detected before they become the source of significant under-performance or cause failure of the processing system.
One common diagnostic system for diagnostically testing fluid control valves, such as pneumatically actuated valves, includes providing a pressure sensor to sense varying control pressures at the input of the valve actuator and a position sensor to sense movement of the valve plug. The valve is then operated through a test operation cycle by supplying a controlled variable fluid pressure to the input of the valve actuator. During the test operation cycle, the valve plug is moved through a desired range, normally from a fully opened position to a fully closed position and returned from the fully closed position to the fully opened position. At the same time, the pressure sensor provides an output signal which corresponds to varying pressure at the valve actuator input, and the position sensor provides an output signal corresponding to movement of the valve plug. The respective output signals of air pressure at the actuator and of valve plug or valve stem position are then processed to derive data that may then be used in a variety of ways to diagnose the operational characteristics of the valve and provide operators with an indication of possible repair needs.
The diagnostic system is often used to test a valve that is already installed in the field. In this case, the position sensor is fixedly mounted somewhere to the valve so as to be able to measure movement of either the flow control member itself or to the measure the motion of a component with movement directly correlated with movement of the flow control member, such as a valve stem or actuator stem.
Various methods and apparatus have been used to mount the position sensor to the valve assembly. Often, a mounting assembly for the position sensor is simply improvised in the field using non-standardized arrangements and mechanism. A difficulty with these improvised mounts, however, is that they can take excessive time to plan and/or install, thereby losing precious time, for example, during a maintenance shut-down in an oil refinery. Some mounting assemblies are known that are arranged to mount the position sensor to the yoke of the actuator. However, deflection of the diaphragm casing cannot be obtained with such a mounting assembly. Other mounting assemblies are known that have a mount with a magnetic base, which requires a flat, ferrous surface to attach to. However, many valve designs do not have one or both of these features, and thus the usability of this mounting assembly is severely limited to only certain valves.
One mounting assembly used in the past included a toggle clamp fixed to a base plate used to clamp the base plate to the bolt flange of an actuator housing. However, this mounting assembly was limited in the range of sizes and/or shapes of valve and/or actuator housings that it could be mounted to and also maintain a desired level of stability.
Another mounting assembly used in the past included a pair of adjustable grip pliers used to clamp a base plate directly to the bolt flange of an actuator housing. However, this mounting assembly often provided less than desirable stability for the position sensor.
It is believed that, until now, there has been no standardized method or apparatus for mounting the position sensor to the valve assembly when setting up the valve testing system that provides a standardized, quick, and easy system for attaching the position sensor to nearly any standard type of process control valve so as to be able to obtain a full complement of movement readings from the valve and provide improved stability of the position sensor.